Should torch always be over metal to fire ?

[bad-rat-57]

Is there any concerns about where the plasma torch is fired ? Should the torch always be over metal when fired. I'm wondering if there will be problems with the electronics by having the torch fired in air if you were to lead into the side of the material for instance in cutting thicker plate vs plunge cutting.

[Med-Pac]

You need some contact to metal to get a plasma to fire. You are right to start at the side of thicker plate, if you have a plasma that is not capable of piercing it. You can also do multiple pierces, but it will probably chew up your consumables.

Mike

[jimcolt]

There usually is no reason to fire a plasma torch in air...in fact it dramatically shortens the life of the nozzle when this is done. An air fired arc is developed between the electrode (negative) and the nozzle (positive).....the energy transfers to the nozzle and erodes the orifice. When you fire the torch within striking distance of the workpiece...the arc transfers very quickly to the workpiece, dramatically reducing heat load to the nozzle orifice. Be sure (when piercing) to have the torch at an adequate distance from the workpiece to ensure that molten blowback does not damage the nozzle or shield......but not too far away!

Jim Colt